Field Measurement of Sediment Oxygen Demand - Case Study in Tidal Keelung River

The sediment oxygen demand (SOD) is the rate of oxygen consumption exerted by the bottom sediment to the overlaying water - due to both the respiration of the benthic biological communities and the biochemical degradation of organic matter. The SOD is often a major component of the dissolved oxygen (DO) budget and hence a key parameter in mathematical models of water quality particularly in relatively shallow water, therefore the measurement of SOD is an important issue for developing the DO module. The Keelung River is one of the major branches of the Danshuei River estuarine system, which runs the metropolitan capital city of Taipei, Taiwan, China and receives a large of amount of wastewater. The dissolved oxygen concentration is generally low in the tidal portion of the Keelung River. Hypoxia occurs often, particularly during low-flow period in summer season. Sediment oxygen demand (SOD) amounts to a significant value, hence increasing the total oxygen demand load of the river. The present work reports laboratory SOD made on grab sediment core samples in situ that are undisturbed. The results reveal that SOD values fluctuate with season variation and are higher in summer due to high temperature effect. It was found in the laboratory tests that the average SOD (at 20 degrees C) value is 0.76 g/m(2)/day and the maximum SOD (at 20 degrees C) value reaches 1.58 g/m(2)/day. Comparisons of the results with those of studies in other estuaries and shallow coastal habitats show that the ranges and means of this study are reasonable.